The present invention relates to a dual-mode telephone system, i.e. a telephone system that can be used both with a public network and also with a private network. In such a system, the telephones used are mobile telephone sets. An object of the invention is to increase the reliability of the various components of the system.
Public mobile telephone systems are known that comprise base stations distributed over an area of land and mobile telephone sets suitable for entering into communication with the base stations. The principle whereby they enter into communication is as follows: when a mobile telephone set is initialized, a message is transmitted for recognizing and identifying the mobile telephone set, and then the mobile telephone set cyclically transmits a location message to the base stations.
Since users of mobile telephone are mobile, it is necessary to keep track of them so as to be able to connect with them at all times. Tracking is achieved by the location signal being transmitted cyclically or continuously. The various base stations receive the location signal and, as a function of the signal level received by each of them, one of the base stations is designated as being the base station which should preferably be in communication with the mobile telephone set. As the user moves, the designation of the base station can change from place to place. The recognition and identification signals, the location signals, and the speech signals are transmitted from the mobile stations to the base stations and vice versa by means of radio transmission of phase and/or frequency modulated carriers. In the context of a public use, the frequency ranges of the modulated carriers are standardized: e.g. they are 900 MHz in GSM, and 1800 MHz in DCS. Other frequency ranges are available for other standards and protocols.
It has become apparent that it would be useful to transpose that type of system for private use. In practice, the same kind of base station equipment has been made available to private individuals, with operation being identical except that the frequency range is then confined to the frequency ranges available for use by private individuals (generally 27 MHz).
Other ways of using mobile telephones are known. In particular, in France, France Txc3xa9lxc3xa9com used to distribute a xe2x80x9cPhonepointxe2x80x9d type of mobile telephone known as xe2x80x9cBibopxe2x80x9d. That mobile telephone can also be used in dual (public and private) mode, and, at the beginning of a session, an identification message is transmitted. However, location messages are not cyclically transmitted. With that type of mobile telephone, the user must not move out from the proper reception range of the base station that recognizes the user at the beginning of a session. In practice, public use sessions are of limited duration, e.g. they are limited to four hours. Beyond that time, tracking is lost. The base station no longer knows the location of the mobile telephone set and no longer forwards incoming calls to it.
Because of the constraints constituted by limiting movement and by limiting session duration, that system is difficult to use.
Therefore, only one dual-mode system remains, namely the system first mentioned above.
The equipment implemented in such systems is of finite life-span. The more frequently the equipment is used, the shorter its life-span. In a dual-mode system, since the equipment is used continuously, it wears more rapidly.
An object of the invention is to increase the life-span of the equipment and to reduce its electricity consumption to as low as possible, and also reduce all radio transmission that occupies frequency space continuously.
In the invention, this object is achieved by making provision such that, in private-use operating mode, the location messages sent cyclically or continuously by the mobile telephone set to the private base station are no longer transmitted when the mobile telephone set is physically and electrically connected to the private base station, in particular when it is hooked thereon to cause its battery to be electrically recharged.
The invention thus provides a dual-mode telephone system comprising a private base station, base stations of a public network, and a mobile telephone, the mobile telephone being provided with a switch-over switch for going from an operating mode in which the private base station is used to an operating mode in which a public base station is used and vice versa, and including a circuit for transmitting a location signal to a base station, the private base station being provided with physical holding means and with electrical connection means respectively for physically holding and for electrically connecting the mobile telephone, said system including a detector for detecting that the private telephone is held on the private base station, and a control circuit for transmitting a command to cease transmission of said location signal, the mobile telephone including a slave circuit for modifying its operating mode as a function of this command.